
public class Solution {
    public static class ListNode {
        int val;
        ListNode next = null;

        ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode Merge(ListNode list1,ListNode list2) {
        ListNode head = new ListNode(-1);
        ListNode root = head;

        while(list1!=null && list2!=null){
            if(list1.val<=list2.val){
                head.next = list1;
                head  = list1;
                list1 = list1.next;
            }else{
                head.next = list2;
                head = list2;
                list2 = list2.next;
            }
        }
        if(list2!=null){
            head.next = list2;
        }
        if(list1!=null){
            head.next = list1;
        }
        return root.next;
    }
    public static void main(String args[]){
         Solution S = new Solution();
         ListNode head =new  ListNode(-1);
         ListNode head1 = new ListNode(-2);
        ListNode head_1 = head1;
        for(int i=3; i<5;i++){
            head1.next = new ListNode(i);
            head1 = head1.next;
        }
        ListNode head_ = head;
        for(int i=0; i<5;i++){
            head.next = new ListNode(i);
            head = head.next;
        }
        S.Merge(head_,head_1);
    }
}